1. Field of the Invention
This invention relates to a process for producing an aqueous liquid laundry detergent composition of desired viscosity and containing nonionic and anionic surfactants.
2. Description of the Related Art Including Information Disclosed Under 37CFR 1.97 and 1.98.
Laundry detergent compositions are sold as either solid, i.e., powder or granular compositions, or liquid compositions. The advantages of liquid over solid compositions are that the caking tending to occur with solid compositions is avoided, the liquid composition is more easily dispersed in wash water, and a liquid is more easily measured and added to the washing machine without spillage than is a solid composition. In addition, larger percentages of nonionic surfactants can be incorporated in liquid detergents than in powdered detergents, resulting in greater effectiveness of liquid detergents in removing oily and greasy soils.
A class of liquid laundry detergent compositions comprising an aqueous medium in which is dissolved a sodium carbonate builder, a surfactant blend comprising two ethoxylated long chain alcohol nonionic surfactants, and two sulfated ethoxylated long chain alcohol anionic surfactants, one nonionic and anionic surfactant containing a larger average number of ethoxy groups per molecule than the other nonionic and anionic surfactant, has been found to have superior freeze/thaw and high/low temperature stability as well as excellent detergency, i.e., cleaning ability. However, to achieve a viscosity of this type of liquid detergent within certain desirable limits, it is often necessary to incorporate in the composition additional components such as a hydrotrope, e.g., alcohol or sodium xylene sulfonate, or a high molecular weight polymer viscosity control agent, which materials may detract from the otherwise desirable properties of the composition. Thus, any method for achieving a desired viscosity while eliminating or reducing the need for the use in the composition of a hydrotrope and/or polymeric viscosity control agent is very desirable.
U.S. Pat. No. 4,464,292, issued Aug. 7, 1984 to Lengyel, discloses mixtures of an ethoxylated long chain alcohol nonionic surfactant and an ethoxylated long chain alcohol sulfate anionic surfactant for use in laundry detergents. Also disclosed is the preparation of such mixtures by partially sulfating the nonionic surfactant with concentrated sulfuric acid.
U.S. Pat. No. 5,004,557, issued Apr. 2, 1991 to Nagarajan et al., teaches aqueous liquid laundry detergent compositions comprising a surfactant, a water-soluble sequester builder, and 0.1 to 2% of a homopolymer or copolymer of acrylic acid having a molecular weight in excess of 100,000 as an anti-redeposition and viscosity control agent. The surfactant may be anionic such as an alkylbenzenesulfonate, nonionic such as a condensation product of ethylene oxide with a C.sub.8 -C.sub.18 primary or secondary aliphatic alcohol, amphoteric such as an N-alkylamino acid, or a combination of such surfactants.
U.S. Pat. No. 5,308,530, issued May 3, 1994 to Aronson et al., discloses a liquid detergent composition comprising a surfactant which may be anionic, nonionic, cationic, zwitterionic or ampholytic, or any combination thereof; a calcium-stabilized enzyme; and as a builder or anti-redeposition agent, a copolymer of an unsaturated carboxylic acid and a hydrophobic monomer prepared by solution polymerization.
Pending U.S. patent application Ser. No. 08/851,034, filed May 5, 1997, discloses and claims liquid laundry detergent compositions comprising a sodium carbonate detergent builder; and a surfactant blend of two anionic surfactants, one of which has the formula R--O--(CH.sub.2 CH.sub.2 O).sub.3 SO.sub.3 M and the other the formula R--O--(CH.sub.2 CH.sub.2 O).sub.7 SO.sub.3 M, where R is a C.sub.10 -C.sub.16 alkyl group and M is an alkali metal or ammonium cation; and two nonionic surfactants, one of which has the formula R--O--(CH.sub.2 CH.sub.2 O).sub.3 --H and the other the formula R--O(CH.sub.2 CH.sub.2 O).sub.7 --H where R is a C.sub.10 -C.sub.16 alkyl group.
Pending U.S. application Ser. No. 08/906,440, filed Aug. 5, 1997, discloses and claims compositions similar to those of Ser. No. 08/851,034 described in the previous paragraph except that the compositions also contain an amphoteric surfactant.